1. Field of the Invention
The invention relates to an improved method for stabilizing pyrophoric catalyst. The method relates to sealing the catalyst in containers by means of a gelatinized starch seal. The invention also relates to an improved method of regenerating catalyst or reclaiming metallic components from spent hydrotreating catalyst.
2. Description of Other Relevant Methods in the Field
Spent hydrotreating catalyst are pyrophoric when dumped from a reactor. The spent catalyst is unpredictable as to when it will spontaneously combust on exposure to air. Some catalyst begins to burn immediately; some catalyst begins to burn after a few days exposure; while some catalysts may begin to burn only with time after dumping in a hazardous waste dump. Piles of ambient temperature catalyst have been later observed to smolder, reaching temperature of 500.degree. F. The pyrophoric nature of hydrotreating catalyst has been attributed to the exothermic oxidation of iron sulfides deposited on the catalysts.
Because the relative propensity of these catalysts to spontaneously ignite is unknown, it is necessary to take full precautions when handling all such catalyst. Full precautions include minimizing contact with air during catalyst handling.
Such precautions have included contact with water or steam. It has also been suggested that a silicone base spray be applied to the catalyst. In the case of water treatment the precaution is temporary. In the case of silicone spray the precaution is expensive. Unfortunately, these precautions degrade the catalyst for regeneration or metal reclamation.
The stabilizing of pyrophoric material is known in the art.
Applicants personal knowledge of the state of the art is that pyrophoric hydrotreating catalyst is dumped into air-tight sealable 52 gallon drums or four drum size bins. A piece of dry ice is placed in each container to generate an inert gas and thereby exclude air before sealing the container. The containers are then shipped for regeneration, metals reclamation or burial as hazardous waste.
T. Y. Yan U.S. Pat. No. 4,650,495 teaches a method for stabilizing heated and dried low rank coal. The method concerns treating the coal particles with a pyrophoric protection fluid. The pyrophoric protection fluid comprises petroleum residual oil, heavy oil, a mixture of tall oil and rosin, gelatinized starch or combination thereof in an amount of about 0.01 weight percent to about 5 weight percent of the coal particles. The method can be used in other applications where dust such as grain dust and wood dust presents a fire and explosion hazard. In one embodiment, gelatinized starch is preferred,
T. Y. Yan U.S. Pat. No. 4,642,196 teaches a method for controlling dust and spontaneous combustion in the drying, handling, transporting and storing of coal. The dust is a result of degradation caused partly by the oxidation of mineral matter, particularly iron sulfide contained in cleavage veins of coal and similar fuels. The method concerns spraying an inhibiting amount of an aqueous solution consisting essentially of gelatinized starch over the coal. All types of starch are applicable including starch derived from corn, wheat, sorghum, rice, barley, potato, tapioca and cassava. Starches rich in amylopectin are more effective, e.g. corn, barley and rice derived starches. It was found that starch solutions were significantly more effective than petroleum resids in preventing and controlling dust. It was also found that coal so treated could be combusted without undesirable combustion products such as salts.
C. H. Leale et al U.S. Pat. No. 4,424,291 teaches an adhesive for corrugated paperboard comprising 2 to 95 weight percent gelatinized starch.
R. K. Graham U.S. Pat. No 4,402,736 teaches a method of agglomerating mineral fines such as iron ore fines by means of pelletizing the fines with gelatinized starch.
E. G. Sammak et al U.S. Pat. No. 4,138,518 teaches a textile composite and method for making the same. The composite comprises gelatinized starch. The patent also teaches fire retardant textile coatings.